The purpose of this research program is to complete a multidisciplinary preschool early intervention study and to extend intervention efforts into the public schools for randomly selected subgroups of children. The children who are participating in the preschool program have been identified at birth as being at high risk for socioculturally caused mental retardation, estimated at causing 70/85% of diagnosed mental retardation in this country. Longitudinal evaluations to date have confirmed that many of the randomly assigned control group children are showing declines in IQ over time to the level of borderline mental retardation by as early as three years of age. Delayed language development has been implicated as a plausible major contributor to the decline in measured intellectual performance. Other domains of longitudinal assessment include: (1) demographic and home information, (2) health and physical development, (3) maternal attitudes, and (4) social interaction patterns. The proposed school age intervention program will use a diagnostic-prescriptive special education model with implementation of supplementary curricula under the supervision of a home school resource teacher. Research projects on the effects of this model are proposed in the areas of intelligence-language and adaptive-social behavior. Laboratory and social-ecology research strategies are proposed to measure children's behaviors in controlled laboratory settings as well as in homes, preschool programs, schools, and neighborhoods. Multivariate statistical analyses on successive measurement occasions, both within and across domains of data, will form the base of data analyses for this program of research. This programmatic research effort should significantly advance our understanding of the physical, psychological, and social mechanisms of progressive development retardation and suggest specific ways in which that retardation can be prevented.